Temperature responsive device



Nov. 27, 1945. v. WEBER TEMPERATURE RESPONSIVE DEVICE Filed Nov. 2 1943 INVENTOR Vzc 7'02 (0);: BER

Patented Nov. 27, 1945 UNITED STATES PATENT OFFICE Robertshaw Thermostat Company, Youngwood, Pa., a corporation of Pennsylvania Application November 2, 1943, Serial No. 508,735

12 Claims.

This invention relates to control apparatus and, more particularly, to snap-action mechanism for controlling temperature, pressure or other physical conditions.

An object of the invention is to insure regulation of the controlled operation by the control apparatus within a reasonable approximation of the control setting.

Another object of the invention is to lessen the probability of undesired or hazardous conditions being created by failure of normal switch-contact operation.

Another object of the invention is to secure a uniform differential throughout the range of control settings when normal operation is superseded by delayed control action.

Another object of the invention is to utilize structure in common for normal and delayed actionof the control apparatus.

Other objects and advantage will become apparent from the following description taken in connection with the accompanying drawing, wherein:

Fig. 1 is a plan view of the apparatus;

Fig. 2 is a side elevation with portions of the housing of the apparatus broken away and showing the switch elements in one position;

Fig. 3 is a plan view, similar to Fig. 1, but with the housing cover removed;

Fig. 4 is a side elevation of the structure shown in Fig. 3 but with the switch elements in a position other than that shown in Fig. 2;

Fig. 5 is an end view of the apparatus; and

Fig. 6 is a partial section taken on the line 6-6 of Fig. 3.

Referring more particularly to the drawing, there is shown an L-shaped frame ID, to which is secured by the screws i2, a channel-shaped cover 14. The arrangement provide a housing having an open end within which a block i6 of insulating material is secured by means of the screws Ill. The frame I0 is adapted to be fastened to a control panel (not .shownl'by means of the lugs 20 through which suitable securing means may project.

The cover 14 is provided with a centrally located boss 22 having an axial opening in which a bushing 24 is secured and provides support for a scale 26 of suitable graduations. Cooperating with the scale 26 is a pointer 28 carried on an adlusting screw 30 which is threaded in an axial opening in the bushing 24 and projects therethrough into the cover I4. The pointer 28 may be provided with spaced arcuate slots 32 through which project clamping screws 34 carried by a within the cover l4 engages the center stud of an expansible and contractible diaphragm 38 and serves to support and move the diaphragm. The interior of the diaphragm 38 is in communication Y with a capillary tube 40 which is partly coiled inside the boss 22 and extends therefrom exterior of the cover where it may be secured by the clamp 4|. The tube communicates with a temperature sensitive bulb 42 and, a is customary in such de-' vices, a contractible and expansible liquid is provided in the bulb and the capillary tube so that upon expansion of the liquid as a result of the heat to which the bulb is subjected the liquid will be forced through the tube into the expansible and oontractible diaphragm thereby actuating it to a sufllcient extent to operate the parts to be described.

A button 44 provided on the face of the diaphragm 38 opposite the stud abuts a depression 46 formed in a main actuating lever 48. This 1ever, which is generally of U-shaped conformation, is provided with a knife-edge 50 serving to connect the legs of the U-shape. The knife-edge 50 is seated in a knife-edged bearing 52 formed on a bracket 54 secured to the inner wall of the i.-shapecl frame I0. The base of the U-shaped actuating lever 48 is recessed at the center portion to provide a seat 55 for one end of a tension spring 56, the other end of which is hooked in an aperture formed in the center cross-bar 58 of an R-shaped control lever 60.

The two legs 62 and 64 of the control lever are provided with knife edges 63 cooperating with knife-edged bearings 65 formed in a channelshaped support 66 extending substantially parallel with the base of the frame 10. The support 66 carries projections 68 which are loosely mounted in the wall of the L-shaped frame l0 adjacent the base thereof and serve to retain the support in position at one end. The support 66 at the opposite end carries an adjusting screw 70 bearing against the base of the frame l0. Lateral displacement of the control lever 60 is prevented by a bracket 72 carried by the inner'wall of the frame l0 and having arms 13 projecting on each side of the legs 62 and 64. It will be apparent that the screw 10 may be adjusted to raise or lower the support 66 and change the tension of the spring 56 as desired.

An inverted V-shaped take-up arm 14 is attached to the control lever 60 rearwardly thereof by means of forwardly projecting spaced lug I6 suitably notched for engagement with oppositely disposed shoulders 18 formed on the legs 62 and 64 of the control lever 60. The take-up arm 14 is further provided with a hook 80 which extends around the underside of the top bar of the R- shaped control lever 60 at the central portion thereof. The hook 80 limits the movement of the take-up arm I4 with respect to the lever 60 and cooperates with the projections I8 to attach it thereto. In addition, a plunger 82 secured to the control lever 60 above the hook 80 extends loosely through the take-up arm I4 and is Provided with a compression spring 84 which normally urges the take-up arm toward the control lever and permits relative movement therebetween.

The take-up arm I4 extends beyond the top bar of the R-shaped control lever 60 and carries a contact block 86 of insulating material mounted thereon for restricted pivotal movement in a horizontal plane. A pair of contact bridges 88 are secured one on each end of the contact block 86 for cooperation with contacts 90, 92, 94 and 96 mounted on the insulating block I6 and projecting exteriorly of the cover I4. It will be observed that in this embodiment the contacts 90, 92 and 90 respectively are provided with terminal connections including screws 98, while the contact 94 is adapted for permanent connection with a conductor, I00. It will be apparent, however,

that such arrangement can be modified as dictated by the circuit arrangement with which the control apparatus is used.

The structure so far described constitutes a snap-action mechanism by which the control lever 60 can efiect contact operation. Thus, as the liquid in the bulb 42 and the capillary tube 40 expands in response to the temperatures prevailing at the point where the bulb is located, the diaphragm 38 will also expand and urge the free end of the main actuating lever 48 toward the knife-edge bearing 65 of the control lever 60. Due to the tension of the spring 56, the control lever 60 and its companion take-up arm 14 will be moved to the right, as viewed in Fig. 2, with a snap-action as the actuating lever 48 moves overcenter past a line between the respective bearings of the two levers. Such'snap-action causes disengagement of the contact bridges 88 and the contacts 90-46 as will be apparent. The position of the levers under these conditions is shown in Fig. 4 wherein it will be apparent that the bias of the spring 56 causing engagement between the contact bridges and contacts 90S6 has been overcome by operation of the thermostat. This open contact position will continue until the diaphragm 38 starts to contract upon cooling of the bulb 42 whereupon a similar overcenter snapaction will occur, but in the opposite direction, to cause contact engagement as th control lever 60 resumes its normal position as shown in Fig. 2.

This invention is more particularly directed to providing sequential operation of a plurality of control devices of which the switching device previously described forms one part. To this end, additional contacts are provided for support by the insulating block I6 and located between the contacts 90-436 and the wall of the L-shaped frame I0. These additional contacts may be two in number and are designated I02 and I04, respectively. The conductor I connects contact 94 with contact I04 permanently, while contact I02 is similar to contacts 90, 92 and 9-6. in having a terminal connection including a screw 88. As indicated diagrammatically in Fig. 3, contacts 80 and 86 may be connectedto line wires I06 and I08, respectively, while contacts 92 and I02 are connected to the heating element I09.

Contacts I02 and I04 cooperate with a contact bridge IIO mounted on an insulating plate II2 which is carried by a flexible member II4 on one end of a secondary lever H6. The secondary lever extends between the arms I3 of the bracket I2 and is provided with lateral projections II8 pivotally mounted in the arms I3 and serving to support the secondary lever H6 and associated parts in position for pivotal movement to engage and disengage the contacts I02, I04 and contact bridge I I0. A compression spring I20 is mounted between the secondary lever IIS and the inner wall of the frame I0 on the side of the pivotal mounting opposite the contact bridge IIO, thus serving to bias the contact bridge out of engagement with the contacts I02 and i04.

In accordance with the principles of this invention, the secondary lever H6 is located in such position that it is beyond the range of the overcenter snap-action of the main' actuating lever 48. Thus, the normal movement of the main actuating lever 48 to eflfect this snap-action can occur without affecting the position or the secondary lever H6 in either contact engaged or disengaged position. In order to provide for operation of the contacts I02, I04 and I I0, by movement of the main actuating lever 48 beyond the range of the overcenter snap action, interengaging means on the main lever 48 and secondary lever H6 are provided.

Such inter-engaging means ma take the form of a rocker E22 mounted on a pivot I23 on the depending portion of an angular arm I24 projecting from the bracket I2 immediately below and inwardly of one of the arms I3 thereof. The rocker I22 extends toward the main actuating lever 48 in position to be engaged thereby when further movement thereof beyond the range of the overcenter snap-action occurs. Preferably, the rocker I22 has a ramp I26 formed thereon and the lever 48 is provided with a lateral projection I28 which will ride along the ramp I26 and serve to tilt the rocket l22 during the further movement of the lever 48. i

As it is desired that contact bridge IIO normally engage contacts Q02, I04 the bias of spring I20 is overcome by a latching arrangement now to be described. The underside of the ramp H6 is engaged by the free end of a U-shaped stripi of spring metal I30 which is secured to the channel-shaped support'fit and has its free end spaced therefrom. The opposite end of the rocker I22 is'thus urged about the pivot i23 toward a projection I32 which is formed on a depressed portion I34 of the secondary lever Ht. Latching engagement between the secondary lever I I6 and the rocker I22 is secured by forming the end of the rocker adjacent the projection I32 with a notch I36 with which the projection I32 may engage. As shown in Fig. 6, the secondary lever I I6 is in what may be termed the unlatched position, notch I36 disengaged from the projection I32. In this position, the spring I20 has biased the lever H8 from normal latched position so that contact bridge I I0 thereon is separated from contacts I02 and I04. A button I38 is provided on the exterior of the cover I4 to reciprocate a pin I40 carried thereby and extending into operative engagement with the lever IIS when the button is depressed. The pin is normally biased out of engagement with the lever IIB by a compression spring I 42 between the button and cover. The pin I40 engages the lever IIS on the side opposite the depressed portion I34 and thus serves to pivot the lever against the bias of the lever spring I20.

In the operation of the control apparatus described it may be assumed that the first set of contacts comprising contact bridges 88 and contacts 9Il96 are engaged and the second set of contacts comprising contact bridge i l0 and the contacts I02-EM are also engaged. Such closed position of the first set of contacts is due to the biasing action of the spring 56 of the overcenter snap-action mechanism, while the similar contact position of the second set of contacts is due to operation of the latching device of lever i The pointer 23 is now set at the temperature it is desired; for the control to operate.

..L '33 circuit for the heating element lill which heats a fluid in thermal contact with the bulb may be traced from the line wire itla, contacts 9@--lll, heating element We, contacts it'll-- conductor contacts l96, to line wire two. As the temperature reaches approximately the level for which is set, the diaphragm will expand sufficiently to cause the overcenter snap-action previously described and move the cont ol lever o the right as viewed in Fig. 2 ing the take-up arm with it to the posishown in Fig. The contact bridges thereupon become disengaged from contacts to, interrupting the flow of curthe power lines tilt to the heatelement So long as iipantied positio it will be interrupted e heating element viii be deenergized. o cooling down the fluid at the bulb diaphragm 161 end or main actuating lever to pass pivot point in the other direction causing the control arm and the take-up arm i l to move to the left fro the position of Fig. to that of Fig. 2 to close the circuit. Such opera-- tion or" opening and closing the first contacts thcontinue hitermittently without any movement occurring on the part of the secon ary lever t it so that the contact bridge 5 it) thereon remains in engagement with the contacts it2--l l.

However, the contact bridges 8:? may under some condition become welded or otherwise im movably fixed to the contacts 93-95 whereupon, regardless of actuation of the control lever til, the current supply to the heating element would not be interrupted. Inthis contingency, the diaphragm would continue to expand, thus moving the main actuating lever 52i beyond the usual range of overcenter snap-action Engagement of the projection in on the main actuating lever G6 with the ramp of rocker l22 would. then occur until projection. lZEEi is caused to ride along the ramp we and depress the rocker M2. The bias of the spring strip lSil is overcome and. the projection i3 2 slips off the rocker causing the secondary lever its to become unlatched. The bias of the spring iZtl thereupon is sufficient to pivot the secondary lever H6 about the. projec time l is thereon and the contact bridge I Ii) separates from the contacts MIL-I04 with a snap action to assume the position shown in Fig. 2.

iii contract permitting the .2

As the circuit of the heating element I09 is element I09 becomes deenergized, although the first contacts remain engaged due to the welding action described. "Thus, the probability of undesired or hazardous conditions being created by failure of normal switch contact operation is lessened. The operation of the secondary lever IIB to disengage the second contacts renders the deenergization of the heating element permanent due to engagement of the projection I32 with rocker I22. Thus, although the diaphragm 38 contracts sufficiently to permit the main actuating lever 48 to return to biased position, the second contacts remain disengaged. Warning is thereby aiforded of the inoperative condition of the first contacts and steps can be taken to remedy such condition.

in order to reengage the second contacts, the

button its is moved inwardly to cause pin M9 to engage and move the lower end of the secondary lever H6, thus overcoming the bias of spring lit and permitting spring arm 53s to tilt the rocker B22 and engage notch 636 with pro-. iection i322. Due to the resumed latching engagement, the secondary lever its will remain in contact position until the main actuating lever it again travels past range of overcenter snap-action thereof and operates the rocker H22 as described.

It will be apparent that the delay period or dii iterential between operation of the overcenter action device operation of the rocker to release the secondary lever lib, may be iu'iiforrn throughout ran e of control gs. That is, while the control is adjustable for normal operation different temperatures, the delayec. control action by the secondar lever will interrupt the circuit at a certain difference for 159 operation, the secondary lever may interrupt the circuit at 398 or, if the setting is 20s", the interruption may occur at 246, there being a to" differential regardless of the initial temperature setting.

From the foregoing it will be apparent that the apparatus can regulate a controlled operation at the desired setting or at a predetermined clifierential. beyond such setting. The specific embodiment herein described is for temperature regula'- tion, but it will be apparent that other physical conditions may be controlled and various circuit arrangements utilized including separate circuits for the first and second contacts. The device is described anol shown as a heat control but could be modified for cold control by rearran ement of the parts as will be apparent. Other modifications and changes may be made in the details of construction and arrangement of parts within the scope of the appended claims Without departure from the spirit of the invention.

I claim:

1. A control apparatus, comprising a first control device movable between controlling positions and being biased to one of said positions, means initially operable for causing movement of said device against its bias from one controlling position to another, a second control device movable between controlling positions by a subsequent operation of said means upon completion of said initial operation, condition responsive means associated with said operable means and having a range of action sufficient to cause sequential operation of said control devices thereby, and manually operable means for resetting saidsecond control device to its unoperated position.

2. A control apparatus comprising a first control device movable between controlling positions, means initially operable for causing movement of said device from one controlling position to another, a second control device movable between controlling positions, snap-action means associated withsaid second device and biasing it to one controlling position, means for holding said second device against its bias in another controlling position, said holding means being rendered ineflective for thepurpose aforesaid by a subsequent operation of said operable means, condition responsive means associated with said operable means and having a range of action suillcient to cause sequential operation of said control devices thereby, and manually operable means for resetting said second device in the position where said holding means is effective.

3. A control apparatus comprising a first control device movable between controlling positions, snap-action means associated with said device and biasing it to one controlling position, said means being operable by overcenter action from biased position for causing movement of said device to another controlling position, a second control device movable between controlling positions, snap-action means associated with'said second device and biasing it to one controlling position, means for holding said second device against its bias in another controlling position, said holding means being rendered inefiective for the purpose aforesaid by said first snap-action means after passing overcenter and condition responsive means associated with ,said first snapaction means and having a range of action suf- 6. A sequential snap-action mechanism "comprising in combination, a control device, a main actuating lever, a control lever for said device,

a tension spring interconnecting said levers for ficient to cause sequential operation of said control devices thereby.

4. A control apparatus comprising a first control device movable between controlling positions, means initially operable for causing movement of said device from one controlling position to another, a second control device movable between controlling positions, snap-action means associated with said second device and biasing it to one controlling position, latching means for holding said second device against its bias in another controlling position, said means including a rocker element positioned in fixed relation with said operable means for engagement thereby subsequent to said initial operation torreleasing said second device to return to its biased position, condition responsive means associated with said operable means and having a range of action sufllcient for said initial operation thereof and thereafter to cause said engagement with said rocker element, and means for adjusting said condition responsive means to different condition settings whereby said initial operation occurs under predetermined conditions with a uniform difierential for said subsequent operation.

5. A sequential snap-action mechanism comprising in combination, a control device, a main actuating lever, a control lever for said device, a tension spring interconnecting said levers for overcenter snap-action of said main lever to actuate said device by said control lever, a pivoted lever spaced from said main lever, a coil spring exerting pressure tending to rotate said pivoted lever, and latching means engageable with said pivoted lever to prevent rotation thereof, said latching means including a portion engageable by said main lever beyond the range of overcenter action thereof.

interconnecting said levers for overcenter snap-action oi! said main lever to actuate said device by said control lever, a pivoted lever located beyond the range oi said overcenter action, a coil spring exerting pressure tending to rotate said pivoted lever, a rocker member having one end adapted for latching engagement with said pivoted lever and another end projecting toward said main lever, yieldable means operative on said projecting end for urging said rocker into said latching engagement and thereby preventing rotation of said pivoted lever, and rocker operating means on said main lever adapted to overcome said yieldable means and release'said latch upon movement or the main lever beyond'said range of overcenter action.

'7. In a snap-action mechanism, the combination with a main actuating lever, a control lever, and a tension spring interconnecting said levers for overcenter snap-action of said control lever upon movement of said main lever, of a secondary lever pivoted intermediate its ends and located beyond the range of said overcenter action, means for biasing said secondary lever to one position, manually operable means for actuating said lever against its bias to another controlling position, yieldable means engaging with said secondarylever and'preventing its return to the first said position, and interengaging portion on said yieldable means and main lever for releasing said secondary lever by movement of said main lever.

8. A control apparatus comprising condition responsive means, a first control device to be actuated thereby, means for transmitting movement from said condition responsive means to said device including a main lever arranged to be actuated by said device, a control lever arranged .to actuate said control device, oppositely disposed bearings for said levers, a tension spring transmitting movement of the main lever to the control lever and imparting overcenter snap-action to the latter as it moves past a line between said bearings, a second control device, a secondary lever connected to said second device and pivoted intermediate its ends, said secondary lever being located beyond the range of said overcenter action, means for biasing said secondary lever to one controlling position, manually operable means for actuating said lever against its bias to another controlling position, yieldable means engaging with said secondary lever and preventing its return to the first said position, and interengaging portions on said yieldable means and main lever for releasing said secondary lever by movement or said main lever beyond said range of overcenter action.

9. A control apparatus comprising condition responsive means, a, first control device to be actuated thereby between closed and open positions to control the condition to which said means is responsive, means for transmitting movement from said condition responsive means to said device including a main lever arranged to be actuated by said device, a control lever arranged to actuate said control device, oppositely disposed bearings for said levers, a tension spring interconnecting said levers for transmitting movement of the main lever to the control lever and imparting overcenter snap-action to the latter as it moves past a line between said bearings, said first control device being biased by said spring to a closed position, a second control device also to be actuated by said condition responsive means between closed and open positions to control the said condition, a secondary lever yield'a'oly connected to said second device and pivoted intermediate its ends, said secondary lever being located beyond the range of said overcenter action, means for biasing said secondary lever to a position in which said second device is in an open position, manually operable means for actuating said lever against its bias to a position in which said second device is in a closed position, yieldable means engaging with said secondary lever and preventing its return to the first said position, said secondary lever maintaining said second device closed irrespective of the open or closed position of said first device by operation of said main lever within said overcenter snap-action range, and intereng'aging portions on said yieldable means and main lever for releasing said secondary lever by movement of said main lever beyond said range of over center action whereby said second control device is actuated to open position and can control the said condition irrespective of whether said first control device remains in a closed position after said overcenter snap-action from biased position has occurred.

I 10. A control apparatus comprising a control device movable between controlling positions, thermally operable means for causing movement of said device from one controlling position to another, a second control device movable between controlling positions by a subsequent operation I of said means upon completion of said thermal operation, and latching means for holding said second device in one position until released by said thermally operable means in said subsequent operation.

11. A control apparatus comprising a control device movable between controlling positions,

thermally operable means for causing movement of said device from one controlling position to another, a second control device movable between controlling positions by a subsequent operation of said means upon completion of said thermal operation, latching means for holding said second device in one position until released by said thermally operable means in said subsequent operation, and means for adjusting said thermally operable means for operation at different temperatures with uniform difierentiai for said subsequent operation.

12. A control apparatus comprising in combi nation, a main actuating lever, a control lever, a tension spring interconnecting said levers, a pivoted lever spaced from the main lever, means tending to rotate said pivoted lever, latching means for preventing rotation of said pivoted lever, means operable upon movement of said main lever beyond a predtermined distance for releasing said latch, and condition responsive means for normally operating said main lever within said distance to cause operation of said control lever without releasing said latch, and being adapted under abnormal conditions for operating said main lever beyond said distance to release said latch.

VICTOR WEBER. 

